Yıldırım, M. Ali; Tuna Yıldırım, Sümeyra; Atalay, Ensar

In this study, the synthesis and characterization of bifunctional CuInO2 thin films that are sensitive to sunlight and can detect carbon monoxide (CO) gas were reported. CuInO2 films were synthesized on fluorine-doped tin oxide (FTO)-coated glass substrates by Successive Ionic Layer Adsorption and Reaction (SILAR) method at 20, 30, and 40 SILAR cycles. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses indicated that the films were in pure hexagonal phase, in dense and uniform nanoplate morphology. UV-Vis analysis revealed that the films exhibited maximum transmittance between 55% and 63% in the visible wavelengths, along with a direct band gap energy ranging from 3.66 to 3.87 eV. The photosensitive behavior of the CuInO2 thin film-based sensors was analyzed in the solar irradiation range of 20–100 mW/cm2. The photodetection results indicated that the sensors exhibited high photosensitivity and fast response speed (τr: 0.6 s, τd: 0.4 s). Gas sensing measurements performed within the temperature range of 30 °C to 135 °C revealed that the sensors exhibited optimum performance at 90 °C. The sensors had high sensitivity, ranging from 2.9% to 65.3%, to CO gas concentrations between 0.1 ppm and 50 ppm, along with good selectivity, baseline stability, and stable repeatability. Moreover, the optimum response and recovery times of the sensors were found to be 32.8 s and 41.8 s for 50 ppm CO gas at 90 °C, respectively. Finally, CuInO2 thin film-based sensors offer excellent sensitivity, selectivity, and long-term stability, combined with a simple fabrication process, making them highly promising for industrial applications.

Yildirim, M. Ali; Ateş, Aytunç

Successive Ionic Layer Adsorption and Reaction (SILAR) was used to form Cd(OH)2 thin films from aqueous cadmium-ammonia complex on glass substrates at room temperature and the thermal annealing effect on thin films was studied. The as-deposited films were annealed at 200, 300 and 400 °C for 1 h in an oxygen atmosphere for conversion from Cd(OH)2 to CdO and change in the structural, optical and electrical properties of the films and the effect of the light on the electrical properties of the films were investigated. The structural and surface morphological properties of the films were studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was found that Cd(OH)2 phase is converted into the cubic CdO films by annealing. The band gap energy values of films decreased from 3.59 to 2.13 eV through increasing annealing temperature. It was found that the current increased with increasing light intensity and CdO films were more conductive than the as-deposited films.